International Publications WO 00/06610, WO 00/06533, WO 00/06658, WO 01/36510, WO 01/40874 and WO 01/74919, the contents of all of which are herein incorporated by reference, discloses a class of polymers obtained from the polymerisation of a number of compounds which possess one or more dienyl end groups. The polymers possess or promise a variety of useful and exciting properties, such as ease of polymerisation, and the ability to “tailor” the properties of the polymer by variation of the “core” group that the end group(s) is attached to. However, the present inventors have found that difficulties can be experienced in polymerising some monomers of the type taught in WO 00/06610. Accordingly, the present inventors have devised improved polymeric systems which, in at least some of their embodiments, enable facile polymerisation to take place and provide polymeric materials exhibiting advantageous and improved properties.